net: parametrize skb_segment unit test to expand coverage

Expand the test with variants

- GSO_TEST_NO_GSO:      payload size less than or equal to gso_size
- GSO_TEST_FRAGS:       payload in both linear and page frags
- GSO_TEST_FRAGS_PURE:  payload exclusively in page frags
- GSO_TEST_GSO_PARTIAL: produce one gso segment of multiple of gso_size,
                        plus optionally one non-gso trailer segment

Define a test struct that encodes the input gso skb and output segs.
Input in terms of linear and fragment lengths. Output as length of
each segment.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/gso_test.c

@@ -4,10 +4,7 @@
 #include <linux/skbuff.h>
 
 static const char hdr[] = "abcdefgh";
-static const int gso_size = 1000, last_seg_size = 1;
-
-/* default: create 3 segment gso packet */
-static int payload_len = (2 * gso_size) + last_seg_size;
+static const int gso_size = 1000;
 
 static void __init_skb(struct sk_buff *skb)
 {
@@ -24,21 +21,121 @@ static void __init_skb(struct sk_buff *skb)
 	skb_shinfo(skb)->gso_size = gso_size;
 }
 
+enum gso_test_nr {
+	GSO_TEST_LINEAR,
+	GSO_TEST_NO_GSO,
+	GSO_TEST_FRAGS,
+	GSO_TEST_FRAGS_PURE,
+	GSO_TEST_GSO_PARTIAL,
+};
+
+struct gso_test_case {
+	enum gso_test_nr id;
+	const char *name;
+
+	/* input */
+	unsigned int linear_len;
+	unsigned int nr_frags;
+	const unsigned int *frags;
+
+	/* output as expected */
+	unsigned int nr_segs;
+	const unsigned int *segs;
+};
+
+static struct gso_test_case cases[] = {
+	{
+		.id = GSO_TEST_NO_GSO,
+		.name = "no_gso",
+		.linear_len = gso_size,
+		.nr_segs = 1,
+		.segs = (const unsigned int[]) { gso_size },
+	},
+	{
+		.id = GSO_TEST_LINEAR,
+		.name = "linear",
+		.linear_len = gso_size + gso_size + 1,
+		.nr_segs = 3,
+		.segs = (const unsigned int[]) { gso_size, gso_size, 1 },
+	},
+	{
+		.id = GSO_TEST_FRAGS,
+		.name = "frags",
+		.linear_len = gso_size,
+		.nr_frags = 2,
+		.frags = (const unsigned int[]) { gso_size, 1 },
+		.nr_segs = 3,
+		.segs = (const unsigned int[]) { gso_size, gso_size, 1 },
+	},
+	{
+		.id = GSO_TEST_FRAGS_PURE,
+		.name = "frags_pure",
+		.nr_frags = 3,
+		.frags = (const unsigned int[]) { gso_size, gso_size, 2 },
+		.nr_segs = 3,
+		.segs = (const unsigned int[]) { gso_size, gso_size, 2 },
+	},
+	{
+		.id = GSO_TEST_GSO_PARTIAL,
+		.name = "gso_partial",
+		.linear_len = gso_size,
+		.nr_frags = 2,
+		.frags = (const unsigned int[]) { gso_size, 3 },
+		.nr_segs = 2,
+		.segs = (const unsigned int[]) { 2 * gso_size, 3 },
+	},
+};
+
+static void gso_test_case_to_desc(struct gso_test_case *t, char *desc)
+{
+	sprintf(desc, "%s", t->name);
+}
+
+KUNIT_ARRAY_PARAM(gso_test, cases, gso_test_case_to_desc);
+
 static void gso_test_func(struct kunit *test)
 {
 	const int shinfo_size = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	const struct gso_test_case *tcase;
 	struct sk_buff *skb, *segs, *cur;
+	netdev_features_t features;
 	struct page *page;
+	int i;
+
+	tcase = test->param_value;
 
 	page = alloc_page(GFP_KERNEL);
 	KUNIT_ASSERT_NOT_NULL(test, page);
-	skb = build_skb(page_address(page), sizeof(hdr) + payload_len + shinfo_size);
+	skb = build_skb(page_address(page), sizeof(hdr) + tcase->linear_len + shinfo_size);
 	KUNIT_ASSERT_NOT_NULL(test, skb);
-	__skb_put(skb, sizeof(hdr) + payload_len);
+	__skb_put(skb, sizeof(hdr) + tcase->linear_len);
 
 	__init_skb(skb);
 
-	segs = skb_segment(skb, NETIF_F_SG | NETIF_F_HW_CSUM);
+	if (tcase->nr_frags) {
+		unsigned int pg_off = 0;
+
+		page = alloc_page(GFP_KERNEL);
+		KUNIT_ASSERT_NOT_NULL(test, page);
+		page_ref_add(page, tcase->nr_frags - 1);
+
+		for (i = 0; i < tcase->nr_frags; i++) {
+			skb_fill_page_desc(skb, i, page, pg_off, tcase->frags[i]);
+			pg_off += tcase->frags[i];
+		}
+
+		KUNIT_ASSERT_LE(test, pg_off, PAGE_SIZE);
+
+		skb->data_len = pg_off;
+		skb->len += skb->data_len;
+		skb->truesize += skb->data_len;
+	}
+
+	features = NETIF_F_SG | NETIF_F_HW_CSUM;
+	if (tcase->id == GSO_TEST_GSO_PARTIAL)
+		features |= NETIF_F_GSO_PARTIAL;
+
+	segs = skb_segment(skb, features);
 	if (IS_ERR(segs)) {
 		KUNIT_FAIL(test, "segs error %lld", PTR_ERR(segs));
 		goto free_gso_skb;
@@ -47,32 +144,30 @@ static void gso_test_func(struct kunit *test)
 		goto free_gso_skb;
 	}
 
-	for (cur = segs; cur; cur = cur->next) {
+	for (cur = segs, i = 0; cur; cur = cur->next, i++) {
+		KUNIT_ASSERT_EQ(test, cur->len, sizeof(hdr) + tcase->segs[i]);
+
 		/* segs have skb->data pointing to the mac header */
 		KUNIT_ASSERT_PTR_EQ(test, skb_mac_header(cur), cur->data);
 		KUNIT_ASSERT_PTR_EQ(test, skb_network_header(cur), cur->data + sizeof(hdr));
 
 		/* header was copied to all segs */
 		KUNIT_ASSERT_EQ(test, memcmp(skb_mac_header(cur), hdr, sizeof(hdr)), 0);
 
-		/* all segs are gso_size, except for last */
-		if (cur->next) {
-			KUNIT_ASSERT_EQ(test, cur->len, sizeof(hdr) + gso_size);
-		} else {
-			KUNIT_ASSERT_EQ(test, cur->len, sizeof(hdr) + last_seg_size);
-
-			/* last seg can be found through segs->prev pointer */
+		/* last seg can be found through segs->prev pointer */
+		if (!cur->next)
 			KUNIT_ASSERT_PTR_EQ(test, cur, segs->prev);
-		}
 	}
 
+	KUNIT_ASSERT_EQ(test, i, tcase->nr_segs);
+
 	consume_skb(segs);
 free_gso_skb:
 	consume_skb(skb);
 }
 
 static struct kunit_case gso_test_cases[] = {
-	KUNIT_CASE(gso_test_func),
+	KUNIT_CASE_PARAM(gso_test_func, gso_test_gen_params),
 	{}
 };